Kinetics of amyloid beta monomer-to-oligomer exchange by NMR relaxation.
Kinetics of amyloid beta monomer-to-oligomer exchange by NMR relaxation.
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DOI：
10.1021/ja1048253
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发表时间：
2010-07-28
影响因子：
15
通讯作者：
Clore, G. Marius
中科院分区：
文献类型：
--
作者：
Fawzi, Nicolas L.;Ying, Jinfa;Torchia, Dennis A.;Clore, G. Marius
最近的研究表明，淀粉样蛋白β(Aβ)的非纤维寡聚体是阿尔茨海默病的主要毒性物种，这使得Aβ寡聚体成为密集研究的对象。然而，很难对这些状态进行详细的结构和动力学表征。在这里，我们使用核磁共振弛豫测量来解决Aβ(1-40)的单体和大的、多态的低聚物种之间的交换动力学。在单体和核磁共振不可见的可溶低聚物之间建立了稳定的假平衡后，在多个磁场下记录了几个肽浓度的15N-R2和1HN-R2数据。15N-和1HN-R2的增加是蛋白质浓度的函数，与核和磁场无关，并且沿着肽链只显示出很小程度的变化。这种现象是由于单体单向转化为核磁共振不可见的低聚物物种(暗状态)而产生的寿命展宽效应。在总Aβ(1-40)浓度为30 0µM时，这个过程的表观一级速率常数为~3 S−1。通过对两个射频场强下两个偶极耦合自旋交换的McConnell方程与饱和转移剖面的拟合，估计出在紧密结合的中心疏水区，73 S−1和瞬时结合单体1HN-R2速率高达42,000 S−1，在无序区域，如前九个残基，高达30 0 0 S−1.与游离态单体交换的‘暗’齐聚态的多肽的比例为~3%。单体和多态低聚物之间相对快速的交换表明，旨在改变这些物种之间平衡分布的治疗努力可能比极其稳定的纤维形式更成功。
Recent studies implicating non-fibrillar oligomers of the amyloid β (Aβ) peptide as the primary toxic species in Alzheimer’s disease have made Aβ oligomers the subject of intense study. Detailed structural and kinetic characterization of these states, however, has been difficult. Here we use NMR relaxation measurements to address the kinetics of exchange between monomeric and large, polymorphic oligomeric species of Aβ (1–40). 15N-R2 and 1HN-R2 data at multiple magnetic fields were recorded for several peptide concentrations subsequent to the establishment of a stable pseudo-equilibrium between monomeric and NMR invisible soluble oligomeric species. The increase in 15N- and 1HN-R2 rates as a function of protein concentration is independent of nucleus and magnetic field and shows only a small degree of variation along the peptide chain. This phenomenon is due to a lifetime broadening effect arising from the unidirectional conversion of monomer to the NMR invisible oligomeric species (‘dark’ state). At a total Aβ(1–40) concentration of 300 µM, the apparent first order rate constant for this process is ~3 s−1. Fitting the McConnell equations for two dipolar-coupled spins in two-site exchange to transfer-of-saturation profiles at two radiofrequency field strengths gives an estimate for koff of 73 s−1 and transiently-bound-monomer 1HN-R2 rates of up to 42,000 s−1 in the tightly bound central hydrophobic region and ~300 s−1 in the disordered regions such as the first nine residues. The fraction of peptide within the ‘dark’ oligomeric state undergoing exchange with free monomer is calculated to be ~3%. The relatively rapid exchange between the monomer and the polymorphic oligomeric form suggests that therapeutic efforts aimed at altering the equilibrium distribution between these species may be more successful than for the extremely stable fibril form.
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影响因子：
2.9
作者：
Petkova, AT;Yau, WM;Tycko, R
通讯作者：
Tycko, R
DOI：
10.1073/pnas.262663499
发表时间：
2002-12-24
影响因子：
11.1
作者：
Petkova, AT;Ishii, Y;Tycko, R
通讯作者：
Tycko, R
影响因子：
2.4
作者：
Lee, Chiu Fan;Loken, James;Vaux, David J.
通讯作者：
Vaux, David J.
DOI：
10.1073/pnas.0812033106
发表时间：
2009-05-05
影响因子：
11.1
作者：
Paravastu, Anant K.;Qahwash, Isam;Tycko, Robert
通讯作者：
Tycko, Robert
影响因子：
64.8
作者：
Tang, Chun;Iwahara, Junji;Clore, G. Marius
通讯作者：
Clore, G. Marius